1. Field of the Invention
The present invention, which has several aspects, is related to the field of light-shaping diffusers and is directed to a seamless master and method of making the same as well as seam replication of diffuser film, i.e. continuous light shaping coating without break point or break mark.
In particular, a first aspect of the present invention is directed to a hollow, cylindrical, seamless, invertable, elastomeric master with integral micro surface structure formed thereon and includes the method of making the same. A second aspect of the present invention is directed to a variable diffuser recording apparatus and process for manufacturing the same, in relation to the first aspect of the present invention. A third aspect of the present invention is directed to a seamless, cylindrical metal master with integral micro surface structure formed thereon and includes the method for forming the same, in relation to the other two aspects of the present invention. A fourth aspect of the present invention is directed to seamless (continuous film) production using the first three aspects.
2. Discussion of the Related Art
Diffuser masters are used to produce a vast assortment of light-shaping diffusers capable of desirably optically affecting light being transmitted therethrough.
Holographic light-shaping diffusers, for example, which are commercially available from Physical Optics Corporation (xe2x80x9cPOCxe2x80x9d) of Torrance, Calif., U.S.A., and sold globally under the trademark LSD(copyright) are diffusers that include xe2x80x9cholographically-recorded,xe2x80x9d randomized surface structures providing the diffuser with high-transmission efficiency, beam-shaping qualities, and the ability to homogenize light. Though they are referred to as xe2x80x9cholographically-recorded,xe2x80x9d they are preferably recorded using only one beam.
Further in that regard, U.S. Pat. No. 5,365,354 to Jannson et al. (assigned to POC), hereby incorporated by reference, discloses a diffuser having integrally-formed light-shaping diffuser microstructures, where the diffuser is manufactured from commercially available photosensitive medium, such as commercial photoresist, and wherein the photosensitive medium has preselected speckle patterns recorded therein.
Additional light-shaping diffusers are disclosed and described in U.S. Pat. Nos. 5,534,386 and 5,609,939 (both to Petersen et al. and assigned to POC) which are also hereby incorporated by reference. The methods taught in both of the Peterson patents can be used to produce and replicate internal and/or surface microstructures in a photosensitive medium such as conventional photoresist. The microstructures are able to diffuse light in a highly-efficient, uniform, and controlled manner, otherwise not possible via prior methods.
According to one prior method shown in U.S. Pat. No. 5,151,917 to Perilloux et al., microstructures are disclosed as forming a laminate with a substructure. In our applications, we have found that a laminated structure poses several problems. For example, certain problems associated with such a laminated construction relate to separation of the layers, transmission losses (due to reflection and/or refraction) at interface surfaces, or problems caused by differences in index of refraction values between the joined optical layers and the optical grade epoxy used to join them, or small air bubbles in the epoxy.
Preferably, the microstructures are integrally formed by coherent light in conventional photosensitive material, to produce light-shaping diffusers. Further in that regard, and depending on the angle of distribution, such light-shaping diffusers will achieve between 85% and 92% transmission efficiency, between 365 nanometers (xe2x80x9crunxe2x80x9d) and 1600 nm. Also, the low back-scatter of light-shaping diffuser structures are anti-reflective in nature, utilizing light that would otherwise be wasted due to Fresnel loss.
Underlying principles as to how LSD(copyright) diffusers work are summarized as follows. LSD(copyright) diffusers are replicated from a xe2x80x9cholographically-recordedxe2x80x9d master, typically, with only one beam. The light shaping and diffusing structures that result, completely random and non-periodic, may be thought of as micro lenslets. Moreover, LSD(copyright) diffusers are not wavelength-dependent, and will work in white, monochromatic, coherent, or incoherent light.
Beam-shaping qualities provide LSD(copyright) diffusers with an ability to precisely shape and distribute light. LSD(copyright) diffusers can produce outputs having circular angles ranging from about 0.5xc2x0 to 100xc2x0 and/or elliptical outputs ranging from about 0.2xc2x0 by 5xc2x0 to 110xc2x0 by 90xc2x0.
The ability to homogenize light is important because so-called xe2x80x9chotspotsxe2x80x9d and uneven light-distribution patterns are common problems with such light sources as light-emitting diode (xe2x80x9cLEDxe2x80x9d) sources, filament-based and arc-based sources, and fiber optic and laser light sources. LSD(copyright) diffusers significantly xe2x80x9csmoothxe2x80x9d and homogenize the light from such sources while providing uniform light transmission in such critical applications as liquid crystal display (xe2x80x9cLCDxe2x80x9d) backlights, LED displays, machine vision, automotive lighting, and viewing screens.
However, conventional masters that are used to manufacture the light-shaping diffusers are generally planar and of finite size. Current manufacturing procedures to produce light-shaping diffusers for viewing-screen applications, result in the edge boundaries of such masters overlying, abutting, or being placed adjacent to each other, resulting in associated edge-boundary patterns in the diffusers, called xe2x80x9cseams,xe2x80x9d that are undesirable because they result in xe2x80x9cinterferencexe2x80x9d areas which adversely affect the ability of the diffuser to transmit light through the xe2x80x9cseamxe2x80x9d portions thereof. Also, when mass produced on long continuous sheets of plastic and rolled up for storage, the seams press against other diffusers in the roll, thus ruining them. Moreover, seams are not acceptable in many applications as large high definition displays for military training, Air Force flight simulator, FAA real time traffic control displays and commercial displays.
Recent improvements have resulted in such edge-boundary xe2x80x9cseamsxe2x80x9d in the diffusers being reduced to a very thin line. Nevertheless, even a very thin line in the diffuser adversely affects the ability of the diffuser to be used for current wide-screen applications, some of which may be as wide as 30 feet wide or 40 feet wide, even up to about 100 feet wide, or more, as is currently contemplated by certain well-known entertainment areas throughout the world.
It would therefore be desirable to be able to produce a seamless master, for producing seamless LSD(copyright) diffusers. It would be even more desirable to be able to produce a diffuser of virtually unlimited length, and having a seamless light shaping diffuser surface thereon.
We solved an assortment of problems otherwise associated with diffusers and their associated diffuser-master edge-boundary xe2x80x9cinterferencexe2x80x9d patterns with our present invention which, briefly stated, is a seamless master and method of producing the same. Our invention, briefly summarized, has three aspects.
One aspect of the preferred embodiment is directed to a seamless master, that is cylindrical and of one-piece construction, and which has an integral seamless light-shaping diffuser surface formed on the exterior circumferential surface thereof. Such a seamless master is preferably hollow and is preferably made of a hard metal such as plated nickel.
Another aspect of the invention is directed to an apparatus and process whereby the seamless master, in turn, is manufactured utilizing a prior-made hollow cylindrical, seamless, elastomeric sub-master having the light shaping diffuser surface integrally-formed seamlessly thereon. The preferred elastomer is commercially-available silicone rubber. The seamless light shaping and diffusing surface is integrally formed on the circumferential surface of the hollow seamless elastomeric master. In connection with this particular aspect of our invention, the above-mentioned elastomeric master (elongated and having the appearance of a xe2x80x9csleevexe2x80x9d), and having the seamless light shaping diffuser surface initially integrally-formed on its interior circumferential surface, is invertable, whereby the elastomeric sleeve can be and is inverted to present the seamless integrally-formed light shaping diffuser surface on the exterior circumferential surface of the rubber sleeve.
Another aspect of our invention is directed to an apparatus utilizing a procedure for effecting variable diffuser recording in photosensitive medium. A final aspect of our invention is directed to utilizing the rubber sleeve or nickel cylinder, i.e. replica of rubber sleeve to produce seamless diffuser film on plastic substrates.